<group>
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[FRAMES, DESCRS] = <a href="%pathto:sift.vl_phow;">VL_PHOW</a>(IM) extracts PHOW features from the
image IM. This function is a wrapper around <a href="%pathto:sift.vl_dsift;">VL_DSIFT</a>() and
<a href="%pathto:imop.vl_imsmooth;">VL_IMSMOOTH</a>().
</p><p>
The PHOW descriptors where introduced in [1]. By default,
<a href="%pathto:sift.vl_phow;">VL_PHOW</a>() computes the gray-scale variant of the descriptor.  The
COLOR option can be used to compute the color variant instead.
</p><dl><dt>
Verbose
<span class="defaults">[false]</span></dt><dd><p>
Set to true to turn on verbose output.
</p></dd><dt>
Sizes
<span class="defaults">[[4 6 8 10]]</span></dt><dd><p>
Scales at which the dense SIFT features are extracted. Each
value is used as bin size for the <a href="%pathto:sift.vl_dsift;">VL_DSIFT</a>() function.
</p></dd><dt>
Fast
<span class="defaults">[true]</span></dt><dd><p>
Set to false to turn off the fast SIFT features computation by
<a href="%pathto:sift.vl_dsift;">VL_DSIFT</a>().
</p></dd><dt>
Step
<span class="defaults">[2]</span></dt><dd><p>
Step (in pixels) of the grid at which the dense SIFT features
are extracted.
</p></dd><dt>
Color
<span class="defaults">[GRAY]</span></dt><dd><p>
Choose between GRAY (PHOW-gray), RGB, HSV, and OPPONENT
(PHOW-color).
</p></dd><dt>
ContrastThreshold
<span class="defaults">[0.005]</span></dt><dd><p>
Contrast threshold below which SIFT features are mapped to
zero. The input image is scaled to have intensity range in [0,1]
(rather than [0,255]) and this value is compared to the
descriptor norm as returned by <a href="%pathto:sift.vl_dsift;">VL_DSIFT</a>().
</p></dd><dt>
WindowSize
<span class="defaults">[1.5]</span></dt><dd><p>
Size of the Gaussian window in units of spatial bins.
</p></dd><dt>
Magnif
<span class="defaults">[6]</span></dt><dd><p>
The image is smoothed by a Gaussian kernel of standard deviation
SIZE / MAGNIF.
</p></dd><dt>
FloatDescriptors
<span class="defaults">[false]</span></dt><dd><p>
If set to TRUE, the descriptors are returned in floating point
format.
</p></dd></dl><p>
See also: <a href="%pathto:sift.vl_dsift;">VL_DSIFT</a>(), <a href="%pathto:vl_help;">VL_HELP</a>().
</p></div></group>
